Personal mobile devices may establish LR-WPAN (Low-Rate Wireless Personal Area Networks), so as to perform communication. An example of the LR-WPAN may include a network following the IEEE 802.15.4 standard. The IEEE 802.15.4 standard uses BPSK (binary phase-shift keying) in a 868/915 MHz band, so as to provide a transmission rate of 20 Kbps and 40 Kbps, and the IEEE 802.15.4 standard uses O-QPSK (offset quadrature phase-shift keying) in a 2.45 GHz band, so as to provide a transmission rate of 250 Kbps. The IEEE 802.15.4b standard may also use O-QPSK in an 868/915 MHz band, so as to provide a transmission rate of 250 Kbps.
As one of the networks, among the networks following the IEEE 802.15.4 standard, an MBAN (Medical Body Area Network) system has been designed to provide a flexible platform for wireless networking of other sensors, which are used for monitoring biological data of patients in a health care facility, such as a hospital.
The MBAN system operates in a 2360˜2400 MHz band based upon an IEEE 802.15.4j, and a maximum emission bandwidth is limited to 5 MHz.
In case the MBAN system is operated in the 2360˜2390 MHz band, a transmission power of the MBAN system may correspond to a lower value of 1 mW and 10*log(B) dBm. Herein, B corresponds to a 20 dB emission bandwidth. And, in case the MBAN system is operated in the 2390˜2400 MHz band, a lower value of 20 mW and 10*log(B) dBm, Herein, B corresponds to a 20 dB emission bandwidth.
Since 2360˜2400 MHz corresponds to a frequency band already allocated to another wireless communication system, the MBAN system is operated based upon a cognitive radio technology. The cognitive radio technology refers to a communication technology allowing a network or wireless communication device to actively detect and determine its surrounding communication environment, so as to adaptively change transmission/reception characteristics, such as a frequency band for an optimal communication, transmission power, encoding method, and so on. At this point, when a cognitive radio device detects the usage of another licensed user/primary user in a frequency band the corresponding cognitive radio device intends to use, the device prioritizes its operation by using a method that does not interfere with (or interrupt) the communication of the corresponding users.
In order to do so, when the MBAN is operated in the 2360˜2390 MHz band, as a rule, the MBAN devices are operated inside of a registered health care facility. In case the MBAN devices are moved outside of the facility, the operation of the devices should be stopped, or transmission should be performed by changing the transmission band to the 2390˜2400 MHz band, which is used as the basic band. More specifically, the usage of 2360˜2390 MHz should be limited in accordance with a cooperation between the licensed users, and, when other licensed users use the corresponding based, all operations in this band should be initialized, and the operations should be resumed by newly using the 2390˜2400 MHz band. In some cases, the operations may be resumed by performing channel switch to another channel within the 2360˜2390 MHz band instead of the 2390˜2400 MHz band. Conversely, in case the MBAN devices are operated in 2390˜2400 MHz, the MBAN devices may be used without limitation both inside and outside of the facility.
A procedure for switching channels to another band from a channel currently being used in any one of the 2360˜2390 MHz band and the 2390˜2400 MHz, when the above-described specific situation occurs, and the related frame are yet to be defined in the conventional MBAN system.